Packet networking is a form of data communication in which data packets are routed from a source device to a destination device. Packets can be networked directly between a source node and a destination node, or the packets can be relayed through a number of intermediate nodes. The packets generally include a source address, a destination address and a payload.
FIG. 1 shows a network device 110 connected to a network 100. A client device 120 can also be connected to the network 100. For some networks, the network device 110 is a layer two (OSI model) device and the network 100 includes layer two routers. With the network 100 including only layer two devices, the network 100 appears to the network device 110 to be a transparent bridge. That is, if the network only includes layer two devices, then any client 120 connected to the network 100, appears to the network device 110, to be directly connected to the network device 110.
In some situations, it may be desirable to implement a network with layer three devices. Generally, a layer two device and layer two networks transparently bridge data packets without altering MAC or IP header fields of the data packets, whereas layer three devices generally alter MAC header fields of data packets passing through the layer three devices. The altering of MAC headers of data packets can present problems when interfacing a layer two device with a layer three network.
It is desirable to have a layer three network that allows a network device connected to the network to perceive the network as a transparent bridge. The network device should perceive a client connected to the network, to be connected directly to the network device.